A technology called SMIL (Synchronized Multimedia Integration Language) is a method conventionally known for integrating the content that includes text, still image, video, and audio, and for describing the spatial and time arrangements; and it is standardized by 3WC (World Wide Web Consortium).
SMIL is the description language similar to the hypertext description language HTML becoming widespread via the Internet at present; and yet it is a preferred description language for distributing the multimedia data that includes a video.
The method of distributing the content described in SMIL and stored on a server, to a client via a network, is explained by using FIG. 1.
The client 5 uses the communication protocols such as HTTP to access the server 1 storing SMIL files, acquires the SMIL files describing the content, interprets the acquired SMIL files, and acquires the respective media data being described, that is, the text data, the still image data, the video data, the audio data, and the like.
In specific terms, the client 5 acquires the video data and audio data from the server 2; and it acquires the text data and still image data from the server 3.
The client 5 replays the respective media data (video data, audio data, text data, and still image data) at the appropriate position and time, based on the space and time information described in the acquired SMIL files. Alternatively, the SMIL data and each media data can be stored in the same server.
Next, the example of description of an SMIL file is explained by using FIG. 2.
Referring to FIG. 2, the 1st line <smil> indicates an SMIL document, and the 18th line </smil> indicates the end of the SMIL document. In addition, any information not relating to time are described between the 2nd line <head> and the 9th line </head>. In addition, from the 3rd line <layout> to the 8th line </layout> these are the information showing the spatial layout of the content, for defining the size and position of positioning an object. From the 11th line <par > to the 16th line </par> these are the information showing the time of replaying the content. In addition, the media relating to time are described between the 10th line <body> and the 17th line </body>.
From the 5th line to the 7th line, the regions v, t, and i for positioning the video, the text, and the still image are defined respectively. From the 12th line to the 15th line, the time information for replaying the video, the audio, the text, and the still image, are respectively defined.
Each line from the 12th line to the 15th line includes “src=” which specifies URL for acquiring the media data. In this example, the video and audio are acquired by using RTSP protocols, and the text and still image are acquired by using HTTP protocols.
Moreover, “region=” specifies the position for displaying the media data, and corresponds to the regions specified in the 5th line to the 7th line. For example, since the text data specified in the 14th line is the region id=“t”, it is displayed on the region specified in the 6th line.
The client cannot find out beforehand what kinds of multimedia data are being described in the SMIL files when the content are described in SMIL. In addition to that, it is difficult for the client to decode all kinds of multimedia data assumed.
In addition to that, in the case of using the wireless transmission path for distributing the multimedia data, even if the kinds of multimedia data specified are decodable by the client, because a bandwidth of the wireless transmission path and an error rate change, the multimedia data transmission is made possible at the specified SMIL in some cases while not in others.
In addition to that, the conventional data distribution system is being proposed for distributing the multimedia data. According to this data distribution system, a media receiving terminal apparatus has a decoder acquiring section which acquires a decoder depending on the multimedia data replaying capability. As appropriate, the media receiving terminal apparatus acquires the decoder to replay the multimedia data even if it does not have the multimedia data replay capability specified by the scenario data such as SMIL.
However, the following problems have occurred under the conventional data distribution system when adapted to one-way communication of the media data, such as broadcasting and multicasting.
For the case of distributing the media data via the wireless transmission path, in particular, even if the kinds of multimedia data specified are decodable at the media receiving terminal apparatus, because a bandwidth of the transmission path and an error rate change, the multimedia data transmission is made possible at the specified SMIL in some cases while not in others.
For example, in regard to the third generation cellular phone system, the media data reception of a low bit rate is possible for the user distant from the base station, and that of a high bit rate is possible for the user near the base station.
As this example, the following document is disclosed as the proposal (refer to www.3gpp.org/ftp/TSG_SA/WG4_CODEC/TSGS4—25bis/Docs/S4-030169.zip) by the standardization organization 3GPP of the third generation cellular phone system.
In addition, since the media receiving terminal apparatus such as cellular phone terminal or Personal Digital Assistant already incorporates the decoder implemented using the hardware or the software, therefore, it is no longer possible to acquire and incorporate the required decoder each time.
As for this kind of media receiving terminal apparatus, if a user selects a program including a media data that the user cannot receive, the problem of not being able to receive and replay the media data occurs.